The present invention relates to a method and system for destratifying heat that accumulates near the ceiling in commercial and industrial buildings. It has long been known that in an enclosure air tends to stratify by temperature with hot air near the ceiling and cold air at the floor level. This is a stable situation physically since hot air is lighter and floats on the colder, heavier air. This phenomenon is particularly noticeable in the winter time when temperature variations from floor to ceiling of 20.degree. F. are not unusual in large buildings.
In buildings where it is necessary to continuously exhaust inside air and replenish with outside air, it is possible to destratify the hot air by introducing the cold, outside [replacement] air near the ceiling where the hot air is stratified. In this connection, applicant's earlier issued U.S. Pat. Nos. 3,307,469, 3,318,224 and 3,524,399 disclose ventilating and circulating air systems featuring a distribution fan spaced from an adjustable shutter within a wall of the building, an air distribution tube mounted to the discharge end of the distribution fan and provided with openings throughout for jetting air into the building, and one or more exhaust fans mounted within the wall of the building, such that during the ventilating mode of operation the distribution and exhaust fans are running while the shutter is open causing cool outside air to be propelled down the tube thereafter being discharged through the openings into the interior of the building, the resulting small jets of air being well mixed with the air inside the building by turbulent mixing. In this manner, the heat at the top of the enclosure that normally would be wasted may actually be used to preheat the jets of cooler, incoming air.
In other buildings where little or no "make-up" air is required, other methods are needed to utilize the waste heat stratified at the top of the building. This can be accomplished by thoroughly mixing or homogenizing the air mass within the building so that the temperature will be essentially uniform from floor to ceiling, thus increasing the floor temperature where the people are located to increase comfort while reducing the ceiling temperature as well as reducing heat losses through the roof. The aforementioned mixing of the air mass must be accomplished with as low residual space velocity as is feasible since high velocity increases the feeling of coldness.
Room air warmed through a heat exchanger can be moved with a fan through a conduit to the vicinity of where people are working, and hot air stratified at the top of an enclosure can be collected and moved by a conduit to the vicinity of where people are working and released, either by a single outlet or a plurality of outlets. Such a system, primarily designed for warm air distribution, will not effectively destratify the great mass of unused, waste heat above the level where the people are located.
One system for controlling the flow of ventilating-tempering air into a building to cause the flow of air to remain primarily along the walls, ceilings and floor, to thereby achieve better distribution of incoming air and more uniform room temperature, is disclosed in U.S. Pat. No. 4,055,112 where the ventilating-tempering air is initially introduced into the room along a boundary surface such as a wall or ceiling and nozzles positioned below the ceiling which form air screens or jets below the ventilating-tempering air stream to guide it along the ceiling and down the walls, in conjunction with an intermediate grate-like ceiling of cross lamellae used to air in separating the ventilating-tempering air stream from the center of the room. In general it may be said that this type of system is not readily adaptable to large rooms.
In U.S. Pat. No. 2,046,215 there is disclosed a system for introducing conditioned air into an enclosure at high static pressure for expanding the air to approximately the pressure existing within the enclosure in the form of thin, elongated high velocity streams in a direction substantially parallel to the floor of the enclosure, thus inducing air within the enclosure to move and mix with the air being introduced to attemperate same. Such a system is generally not applicable for destratification.
With the present invention, heat destratification is accomplished with the use of a powered, inflated tube recirculating air system located near the ceiling of the enclosure. Hot air is drawn off the ceiling by the distribution fan and discharged down the tube as "primary" air and thereafter projected through relatively large openings in the bottom of the tube toward the floor. The high velocity jets leaving the tube entrain large quantities of surrounding ceiling air and move this "secondary" air toward the floor. An entrainment factor of ten to one or better is possible achieving a thorough mixing action of the entire room contents effectively destratifying the wasted ceiling heat.